System of optical projection of images by reflex reflected illumination



Dec. 14, 1965 G. ALTMAN 3,222,986

SYSTEM OF OPTICAL PROJECTION OF IMAGES BY REFLEX REFLECTED ILLUMINATION Filed March 6, 1964 5 Sheets-Sheet 1 60 /,E6 I\/ J" J 58 I1 ,fl fl 64 an j I i Fl F 1 Uh LI FIG. I

PHOTOEXPOSE PHOTOSENSITIVE ANTIHALATION 56 f RETROREFLECTING 54 x SPHERES 3O 52 7 BASE F3. RETROREFLECTIVE BASE Dec. 14, 1965 G. ALTMAN 3,222,986

SYSTEM OF QPTICAL PROJECTION OF IMAGES BY REFLEX REFLECTED ILLUMINATION Filed March 6, 1964 5 Sheets-Sheet 2 PHOTOSENSITIVE 5? 65 ANTIHALATION RETROREFLECTING /5 CUBE CORNERS F I 3 3 BASE 63 PH OTO EXPOSE PHOTO- CONDUCTING ANTIHALATION HEAT SENSITIVE REACTANT RETROREFLECTING BASE SPHERES VISIBLE PARTICLES TO DEVELOP,HEAT TO FIX 8 CLEAR ANTIHALATION 7O IZ/ RETROREFLECTIVE BASE PHOTOCONDUCTING ANTlI-IALATION HEAT SENSITIVE REACTANT RETROREFLECTING CUBE F I 5 CORNER Dec. 14, 1965 G. ALTMAN 3,222,986

SYSTEM OF OPTICAL PROJECTION OF IMAGES BY REFLEX REFLECTED ILLUMINATION Filed March 6, 1964 5 Sheets-Sheet 5 MIXTURE OF SIZING 8 RETROREFLECTING SPHERES PAPER BASE FIG? MULTI- COLOR HALFTONE ":4 MIXTURE OF BINDER at 3,0 'g g y .nf RETROREFLECTING SPHERES PAPER E United States Patent Claims. (Cl. 8824) The present application is a division of U.S. patent application Serial No. 249,351, filed, January 4, 1963 for Optical Products, Processes and Devices, in the name of the inventor hereof.

The present invention relates to a system that incorporates products, processes and devices for the projection of images and, more particularly, to the projection of an image by illumination returned from a generally opaque representation, viz. episcopic projection, rather than by illumination transmitted through a generally transparent representation, viz. diascopic projection.

In a typical episcopic projection system, a photographic print or other generally opaque representation is illuminated by light from an adjacent source and an optical image in terms of scattered light from the print is projected by a lens onto a viewing screen. Because the useful scattered light available is proportionately small, the illumination source must be intense and the projection lens aperture must be large. Although it is common experience that such a photographic print is capable of being viewed with ease, for the foregoing reasons its projection image often can be produced only at great inconvenience and expense.

In contrast, in the more usual diascopic projection systern, condensed light from an illumination source is directed through a photographic transparency (e.g. lantern slide or cinematographic film) or other generally transparent representation for projection by a lens onto a viewing screen. Because the useful condensed light available is relatively great, the illumination source intensity may be relatively moderate and the projection lens aperture may be relatively small. Although it is common experience that a transparency may be viewed directly only with difficulty, for the foregoing reasons its projection image ordinarily can be produced conveniently and inexpensively.

The primary object of the present invention is to provide a system that incorporates products, processes and devices involving episcopic projection of improved practicability by associating the representation, of which an image is to be projected with a multiplicity of minute reflex reflecting elements by which illumination incident upon the representation is redirected with controlled or minimum dispersion toward the projection lens. As is well known, a reflex reflecting element may take the form either of: a catadioptic element, usually a sphere, having a forward lens surface for refracting incident radiation and a rearward reflecting surface for returning the radiation through the lens surface; or a corner reflector having three mutually perpendicular reflecting faces which cooperate to return a beam of incident radiation along its path of incidence. Both types of reflex reflecting elements have been termed retroreflectors. A feature of the foregoing retroreflector-representation association is that, if the retroreflecting elements are sufilciently small, they are practically unnoticeable when the representation is viewed directly but are capable nevertheless of a powerful retroreflective action when appropriately positioned with respect to an illumination source and a projection lens.

Another object of the present invention is to provide a system that incorporates products, processes and devices involving an assemblage comprising a retroreflective stratum containing minute elements, a photosensitive stratum that may be developed chemically or physically, and an antihalation stratum interposed therebetween. The antihalation layer prevents interaction of the retroreflective stratum and photosensitive stratum during photoexposure but disappears when the photosensitive stratum is developed.

A further object of the present invention is to provide a system that incorporates products, processes and devices involving the projection of a representation produced by imprinting upon a matrix stratum which is associated with retroreflective elements of the foregoing type.

The matrix stratum, for example, is a suitable paper composed of felted cellulosic fibers or a micro-striated polymer, both of which have outer surfaces capable of receiving pigment (including pencil) and dye (including ink) markings. This object of the present invention contemplates the etfective projection of written material accompanying educational lectures and of photographic half-tone photographs appearing in periodical literature.

Other objects of the present invention will in part' be obvious and will in part appear hereinafter.

The invention accordingly comprises the several components and steps and the interrelations among such components and steps, exemplified in the following detailed" disclosure, the scope of which will be indicated in the appended claims. For a fuller understanding of the nature and objects of the present invention, reference should be had to the following detailed description taken in connection with the accompanying drawing, wherein:

FIG. 1 is a side view, with interior components in dotted lines, of a photographic projection system embodying the present invention;

FIG. 2 illustrates in exaggerated crosssection and perspective, a product undergoing a process, in accordance with the present invention:

FIG. 2A illustrates, in exaggerated, broken-away perspective, an element of FIG. 2;

FIG. 3 is a view, in exaggerated cross-section and perspective, of another product of the present invention;

FIG. 4 illustrates, in exaggerated cross-section and perspective, another product undergoing another process, in accordance with the present invention;

FIG. 5 is a view, in exaggerated cross-section and perspective, of a further product of the present invention;

FIG. 6 is a side view, with interior components in dotted lines, of an alternative projection system embody ing the present invention;

FIG. 7 illustrates, in exaggerated cross-section and perspective, another product of the present invention;

FIG. 8 illustrates, in exaggerated cross-section and perspective, a further product of the present invention; and

FIG. 9 illustrates, in exaggerated cross-section and perspective, another product of the present invention.

Generally, projection of images in accordance with the present disclosure involves a projector and a representation (black-and-white or multi-color) in relative proximity within a unitary housing, and a relatively remote viewing screen, the representation being contiguously associated throughout its area with a multiplicity of minute retroreflecting elements. In conventional fashion, the representation and the viewing screen in optical theory occupy conjugate focal surfaces. The retroreflecting elements, generally no more than 0.1 inch in maximum extent and preferably no more than 0.01 inch in maximum extent, either are hemispherically-clear, hemispherically-metallized refracting spheres or are metallized cube corners. The source of illumination is associated with a beam splitter which, from an optical standpoint, positions the illumination source and the projection lens in coincidence with respect to the representation. The arrangement is such that divergent rays from the illumination source to the representation are returned as convergent rays from the representation to the projection lens. In consequence, even large representations are capable of effective illumination and projection by a light source and a projection lens, both of modest size.

The projecting system of FIG. 1, which is designed primarily for the photographic products of FIGS. 2 to 5, generally includes, in combination, a laminated photographic sheet having a retrorefleotive representation, a projector 22 containing laminated photographic sheet 20, and a relatively remote projection screen 24 of the type having dispersed metallic particles, glass spheres or white pigment as an image viewing matrix. Projector 22 includes a unitary housing 26 having a forward portion 20 and a rearward portion 30 that are intermediately connected by a bellows 32 to provide a light-tight chamber therewithin. Forward portion 23 is mounted upon a sable base 34. Rearward portion 30 is movable on base 34, as by means of rack and pinion 36. Mounted on rearward portion 30 within the housing is a frame 38, by which photographic sheet 20 is positioned. The remaining components of projector 26, which are suitably aflixed within forward portion 28, include an illumination source 40, a beam splitter 42 and an objective lens 44. Beam splitter 42, in the form for example of a halfsilvered mirror, directs light from illumination source to photographic sheet 20 to objective lens 44. Illumination source 40 includes a sealed lamp 46 containing a medial filament, a rearward reflector and a focusing lens 48, by which the solid angle of a diverging cone 49 of illumination is determined. The axis of illumination source 40 and the axis of objective lens 44 are at right angles to each other and at 45 angles to beam splitter 42, the arrangement being such that rays diverging as at 49 from source of illumination 40 toward photographic sheet 20, converge from photographic sheet 20 as at 51 toward objective lens 44. Preferably, the adjustment of illumination source 40 is such that the flux cross-section of radiation generated by the filament of lamp 46 and retrorefiected by sheet 20 approximately fills the stop of lens 44. Preferably the adjustment of objective lens 44 is such that photographic sheet 20 is disposed in its focal surface. It is apparent that by properly adjusting rearward portion 30, images of larger or smaller photographic sheets 20 may be projected onto screen 24.

Sheet 20 of FIG. 1, as shown in FIG. 2 comprises, in laminated sequence, an opaque base stratum 50, a retroreflective stratum 52 containing a multiplicity of minute retroreflecting elements, an initially opaque antihalation stratum 54 and a photosensitive stratum 56. Photoexposure of photosensitive stratum 56 produces a latent image therein, retroreflection from retroreflective stratum 52 being prevented by antihalation stratum 54. Development of photosensitive stratum 56 produces a visible print in stratum 56 and clears antihalation stratum 54. This print has the usual characteristic (H and D) curve (density plotted against log exposure), having transverse upper and lower extreme portions that are outwardly and oppositely directed and a generally oblique intermediate portion, the slope of which is designated by gamma.

Details of the materials of the strata of sheet 20 are as follows. Base stratum is composed either of paper, i.e. a felted sheet of cellulosic fibers, or plastic, for example, a cellulosic polymer such as cellulose nitrate, cellulose propionate or cellulose butyrate. Retroreflective stratum 52 is composed of minute glass spheres that are hemispherically transmitting and hemispherically reflecting, dispersed in a transparent lacquer, as disclosed in: US. Patent No. 2,997,403, issued August 22, 1961, in the name of Charles E. Seright for Reflex Reflective Coating Composition; and US. Patent No. 2,963,378, issued December 6, 1960, in the name of Philip V. Palmquist for Glass Beads Hemispherically Reflectorized With Metallic Coating and Compositions Thereof. Preferably, such spheres (FIG. 2A) are characterized by One hemispheric portion which is clear and the other hemispheric portion which is coated first at 53 with a metal, such as aluminum, and second at 55 with a paint, such as titanium dioxide lacquer, which covers the outer surface of the metal. Antihalation stratum 54 is composed of a polar acting dye which clears in acid or alkali, for example, phenophthalene, Acid blue black (Color Index 246) or Acid magenta (Color Index 692), dispersed in a polymer, for example, an ester such as cellulose acetate. Suitable antihalation compositions are disclosed in US. Patent No. 2,322,006, issued on June 15, 1943, in the name of Scheuring S. Fierke et al., for Photographic Filter and Antihalation Layer. Photosensitive stratum 56 is shown as being a silver halide emulsion. In such an emulsion, one or more of the silver halides, of which silver chloride, silver bromide and silver iodide are examples, are dis persed in a suitable colloidal material, such as gelatine,. agar, albumin, casein, collodion or cellulosic ester. In use, photosensitive stratum 56, after photoexposure to provide a latent image, is developed by silver reduction and fixed by silver halide dissolution in an alkaline environment. The developer generally is alkali active, i.e. active only in alkaline solution, so that its development is accompanied by clearing of antihalation stratum 54. Examples of developers of this type are pyrogallol, hydroquinone, metol, amidol, para-aminophenol and glycin. The fixing agent, for example, is a silver halide solvent such as sodium thiosulfate or sodium thiocyanate. The alkali, for example, is an alkali metal base such as sodium or potassium hydroxide or a nitrogenous base such as ammonium hydroxide or hydroxylamine.

One specific example of the product and process of FIG. 2 involves the following. In the specific product of FIG. 2; stratum 50 is composed of baryta paper approximately 0.001 inch thick; retroreflective stratum 52 is composed of a multiplicity of hemispherically metallized, hemispherically clear glass microspheroids of the type shown in FIG. 2A, having diameters ranging from 10 to 50 microns and a refractive index of at least 1.8, dispersed within a clear melamine-formaldehyde polymer in a distribution that is approximately 0.001 inch thick; antihalation stratum 54, which is composed of an acid azo dye, Methyl red, dispersed in cellulose acetate, is approximately 0.001 inch thick; and silver halide stratum 56 is a moderately high speed, gelatino iodobromide emulsion that is approximately 0.001 inch thick. After photoexposure to provide a latent image in photosensitive stratum 56, the foregoing specific product is processed in the following sequence of steps. The photoexposed product is developed in the following solution for 3 minutes at 20 C.

Water cc 3000 Metol g 3 Sodium sulfite g 44 Hydroquinone g 12 Sodium carbonate g 36 Potassium bromide g 2 During development the antihalation layer clears and a print becomes visible in the photosensitive stratum. After washing for 10 minutes, fixing is effected by immersion in the following solution for 5 minutes at 20 C.

Water cc 3000 Sodium thiosulfate g 240 Sodium sulfite g 15 Acetic acid (28%) cc Borax g 14.5 Potassium alum g 15 After washing for 10 minutes and drying, the resulting print is of good quality for both direct observation and episcopic projection.

The product of FIG. 3, shown generally at 58, includes. in laminated sequence, a support stratum 60, a retro reflective stratum 62, an antihalation stratum 64 and a photosensitive stratum 66. Support statum 60, antihalation stratum 64 and photosensitive stratum 66 are like their counterparts at 50, 54 and 56 in FIG. 1. Retroreflective stratum 62, which is composed of any suitable one of the plastic materials referred to above, presents a multiplicity of minute cube corners, which are embossed in stratum 62 and metallized as at 63. In a specific example of a process involving the product of FIG. 3, details of the materials and steps are identical to those of the foregoing specific example of FIG. 2, except that base stratum 60 is omitted and retroreflective stratum 62, composed of glass or methyl methacrylate approximately 4 inch thick, presents cube corners, approximately A; inch in maximum extent, that are metallized with a coat of aluminum approximately 0.001 inch thick.

It will be understood that in other embodiments of the invention, the gelatino silver halide of photosensitive strata 56 and 66 of FIGS. 2 and 3 are replaced by other photosensitive materials, for example: a ferric composition capable of being developed by potassium ferrocyanide; a diazo material capable of being developed by an alkali; a bichromated material capable of being dilferentially hardened and dyed; a photopolymerizable material capable of being differentially polymerized by incident light as in US. Patent No. 2,948,611, issued on August 9, 1960, in the name of Arthur L. Barney for Photopolymerizable Compositions, Elements and Processes; a photothermographic material capable after photoexposure of being developed by heat, as in US. Patent No. 2,095,839, issued on October 12, 1937, in the name of Samuel E. Sheppard et al., for Photothermographic Composition; or a phototropic material capable of being differentially darkened by light without development, as in US. Patent No. 2,953,454, issued on September 20, 1960, in the name of Elliot Berman for Phototropic Data Storage Capsules and Base Coated Therewith'.

.A particularly pertinent thermographic process is disclosed in US. Patent No. 3,046,128, issued on July 24, 1962, in the name of Robert J. Klinkowski et al., for Thermally Developable Diazotype Photoprinting Material and Production Thereof. In one product embodying the form of FIG. 2, photosensitive stratum 56 contains a diazo compound, e.g. diazotized p-amino-N,N-dimethylaniline, antihalation stratum 54 contains the acid dye, Methyl red, dispersed in cellulose acetate in suflicient quantity to produce opacity, retroreflective stratum 52 contains retroreflective spheres, eg of the type described above in connection with FIG. 2 dispersed at the lower face of antihalation stratum 54, base stratum 50 is composed of paper, the under free face of which is coated with a composition containing: water-100 ml.; 30% aqueous colloidal silica, 0.015 micron particle size-25 ml.; urea-125 g.; guanidine carbonate-50 g.; butadiene-styrene (weight ratio, 40:60) copolymer aqueous emulsion, 48% solids-50 ml. After photoexposure, heating of the product causes transmission of alkali vapor through base stratum 50 and, consequently, development of photosensitive stratum 56 and clearing of antihalation stratum 54.

In another alternative embodiment of the present invention, the product of either FIG. 2 or FIG. 3 is developed and fixed by a so-called diffusion transfer reversal process of the type disclosed in U.S. Patent No. 2,543,181, issued on February 27, 1951, in the name of Edwin H. Land for Photographic Product Comprising a Rupturable Container Carrying a Photographic Processing Liquid. In accordance therewith, the product of either FIG. 2 or FIG. 3 is processed by spreading an aqueous alkaline solution of a silver halide developer and a silver halide solvent between the product \and a receiving sheet. Silver is developed in the photosensitive stratum to produce a negative print and a silver halide complex, formed at the photosensitive stratum, migrates to the receiving sheet to produce a positive print. In one modification of this form of the invention, a retroreflective stratum of the type shown in FIG. 2 or FIG. 3 is provided in the receiving sheet. In another modification of this form of the invention, retrorefiecting microspheroids are spread from the container with the processing solution for association with the receiving sheet after photoexposure and during processing.

FIG. 4 discloses a sheet 68 of a type useful in electrophotography. Sheet 68 includes, in laminated sequence, a base stratum 70, a catadioptric retroreflective stratum 72, a heat sensitive reactant stratum 77, an anti-halation stratum 76 and a photooonductive stratum 74. The associated process involves charging photoconductive stratum 74 uniformly, photoexposing photoconductive stratum 74 to produce a differential electrostatic image, subjecting the electrostatic image to a developer powder, and heating the product in order to fix the powder to the ph otoconductive stratum and to cause heat sensitive reactant stratum to clear antihalation stratum 76.

Photoconductive stratum 74, for example, contains as a photoconductor: a photooonductive oxide, sulfide, selenide, telluride or iodide of cadmium, mercury, antimony, bismuth, thallium, molybdenum, aluminum, lead 'or zinc; or arsenic trisulfide, cadmium arsenide, lead chromate or selenium. Photoconductive stratum 74, for example, contains as a vehicle: an electrically insulating, film forming polymer, having high dielectric constant and high diele=ctric strength such as polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic or guar gum. The thickness 'of photoconductive stratum 74 is not critical but preferably ranges between 0.0003 to 0.002 inch. The relative proportions of ph'otoconduictor to vehicle range between 1:1 and 9:1.. With respect to the remainder of this product, antihalation stratum 76, heat reactant stratum 77, retroreflective stratum 72 and base stratum are analagous to their counterparts in FIGS. 2 and 3. Specifically useful electrophotographic compositions and steps are disclosed in US. Patent No. 2,939,- 787, issued June 7, 1960, in the name of Edward C. Giaimo, Jr., for Exposure of Photochemical Composition; and US. Patent No. 2,993,787, issued July 25, 1961, in the name of Meyer L. Sugarrnan, Jr., for Electrostatic Printing.

The product 'of FIG. 5, like the product of FIG. 4 capable of producing an electrostatic image, comprises, in laminated sequence, an electrically conducting support stratum 78, a retro-reflective stratum 80, an antihalation stratum 82 and a photoconductive stratum 84. The strata are identical to corresponding strata of FIG. 4, except that retroreflective stratum 80 is like corresponding stratum 62 of FIG. 3 and the reactant to clear antihalati-on stratum. 82 is applied from an external source.

In a specific example of the compositions and steps of FIGS. 4 and 5, the base stratum 70 and retroreflective stratum 72 are identical to their counterparts in FIGS. 2 and 3. Antihalation stratum 76 is composed of Methyl red. Photoconductive stratum 68, 0.0005 inch thick, is composed of a blend of: 5 g. of polyvinyl alcohol; and 100 g. of GP. photoconductive zinc oxide. Photoconductive stratum 68 is charged and exposed in conventional fashion. A cloud of developer powder consisting of 200 mesh powdered zinc is directed toward photoconductive stratum 68 in order to produce a visible print. Fixing is elfected with a light spray of a solution of polyvinyl alcoih'ol in water (5% polyvinyl alcohol and water, by total weight). Clearing of antihalation stratum is elfected by aqueous ammonia Vapor.

In another specific example of the compositions and steps of FIGS. 4 and 5, the product consists merely of: a base stratum, 0.001 inch thick, composed of black paper; and a photoconductive stratum, 0.005 inch thick, composed of a blend of 5 g. polyvinyl alcohol and g. of GP. photoconductive zinc oxide. Photoconductive stratum is electrostatically charged and photoexposed in conventional fashion. Development is effected with a cloud of hemispherically reflecting, hemispherically-clear minute spheroids that are in the general range of 200 mesh. These spheroids are of the type shown in FIG. 2A, the outer surface of the reflecting portion, which is coated with a metal, such as aluminum, being coated additionally with a paint, such as titanium dioxide lacquer. Fixing is effected in conventional fashon, for example, by spraying with a transparent lacquer, such as polyvinyl alcohol in acetone. As viewed directly by an observer, the resulting print is in terms of light scattered from a white pigment on a dark background, since normally any incident light theoretically capable of being retroreflected to the eyes of the observer is blocked by the observers head. On the other hand, projection in the apparatus of FIG. 1 results in the production of an episcopic image in accordance with the present invention. In a multicolored image of this type the refracting composition of the spheroids and their backings are of appropriate additive or subtractive colors. In a print of this type, the retroreflective spheroids are distributed in gradually varying concentration per unit area, thereby being characterized by a curve, of density v. l-og exposure, that is similar to the analogous curve of the product of FIG. 2.

FIG. 6 illustrates a novel episcopic system by which subject matter may be projected onto a viewing screen 88 as it is being written or printed by a lecturer, record keeper or other operator on the exposed sheet 90 of a block 92 of sheets. Each sheet 90, as is shown in FIG. 7, comprises a base stratum 94 composed of paper and a coating 96 of retroreflective microspheres dispersed in a surfacing material such as zein or clay. In typical fashion, imprinting is effected by a graphite pencil 98 or the like.

Block 92 is positioned on an exposed and accessible table 100 by a clip 102 which retains the block in position by a suitable spring (not shown). Table 100 is supported by suitable legs 106. Positioned above table 101) by arms 108 is a housing 110 within which the illuminating and projecting components are enclosed and supported. These components include a source of illumination 112 in the form of a sealed beam lamp containing a filament 114, a reflector 116 and a lens 118. A. beam splitter 120 directs divergent light from source of illumination 112 through lens 122 to retroreflective image bearing sheet 90. Lens 122 directs convergent light through beam splitter 120 for deflection by a mirror 124 through an objective lens 126 toward screen 88.

FIGS. 8 and 9 illustrate modifications of the product of FIG. 7. The product of FIG. 8 includes a paper base 130 and a mixture 132 of binder and glass microspheres, analogous in all respects to their counterparts in FIG. 7. On the surface of stratum 132 are imprinted red, green and blue halftone dots for the direct observation and episcopic projection, in the apparatus of FIG. 6, of multicolor halftone prints. The product of FIG. 9 includes: a plastic base 134, into which are embossed metallized cube corners 136; and a pigment or dye receiving coat 138. In one example, plastic base 134 is composed of methyl methacrylate, cube corners 136 are reflectorized with a thin silver film and coat 138 is a depolymerized polymer, such as polyvinyl chloride. Alternately coat 138 is a polymer having microscopic pores or striations or coat 138 includes an abrasive such as carbon powder.

The present invention thus provides a system incorporating products, processes and devices for the episcopic projection of representations in an eflicacious and practicable manner. Since certain changes may be made in the above described product, processes and devices without departing from the scope of the invention herein involved, it is intended that all matter, contained in the above description and shown in the accompanying draw- 8 ing, shall be interpreted in an illustrative and not in a limiting sense.

What is claimed is:

1. A projection system comprising means including a sheet having, as components of said sheet in optical communication, a representation and a multiplicity of minute reflex reflecting elements, said multiplicity of minute reflex reflecting elements each inherently including means for acquiring incident radiation from substantially any one of a multiplicity of inward directions and means for redirecting resulting radiation in substantially the opposite one of a multiplicity of outward directions for the purpose of establishing a selected substantially common path for an incident ray of radiation direct toward said representation and for a resulting ray of radiation redirected by said multiplicity of reflex reflecting elements, said path characteristically being substantially dependent upon the direction of said incident ray and characteristically being substantially independent of the angle of incidence between said incident ray and said sheet, means for directing such radiation into said path from a source, and means for projecting an image of said representation onto a viewing screen in terms of such radiation.

2. A projection system comprising a housing, a support in said housing, a sheet carried by said support, said sheet having, as components of said sheet in optical communication, a representation and a multiplicity of minute reflex reflecting elements, said multiplicity of elements establishing selected substantially common paths for rays of divergent radiation incident upon said sheet and rays of convergent radiation returned by said sheet, each of said common paths characteristically being substantially dependent upon the direction of its incident ray and characteristically being substantially independent of the angle of incidence between said incident ray and said sheet, a source of said divergent radiation, a projector for said convergent radiation, and means for directing said divergent radiation to said sheet and for directing said convergent radiation to said projector, said sheet being substantially in one conjugate focal surface of said projector, an image of said representation being substantially in the other conjugate focal surface of said projector, whereby the brightness of said image is substantially dependent upon said multiplicity of minute reflex reflecting elements and the appearance of said representation when viewed directly is substantially independent of said multiplicity of minute reflex reflecting elements.

3. The projection system of claim 2 wherein said support and said projector are movable relative to eachother in order to adjust the positions of the conjugate focal surfaces with respect to said projector.

4. The projection system of claim 2 wherein said housing is open in the vicinity between said sheet and said source for manual and visual accessibility of said sheet.

5. A projection system comprising, a substantially flat and substantially flexible sheet incorporating in superposition a visible record containing stratum and a reflex reflecting stratum, said visible record constituting a photographic continuous tone, silver print, said reflex reflecting stratum containing a multiplicity of minute reflex refleeting increments, each of said reflex reflecting increments being at most 0.01 inch in maximum extent and including an optically conformed component and a specularly reflecting component that cooperate to predeterminedly receive a beam of radiation incident in a first direction and to redirect said beam of radiation in a second direction, said first direction and said second direction being at substantially a fixed angle with respect to each other substantially notwithstanding the orientation of said visible record stratum and said reflex reflecting stratum, beam splitting means, illuminating means for directing radiation through said beam splitting means in said first direction from a source, objective means for projecting an image of said record reflected by said beam splitting means in terms of radiation in said second direction, and a viewing screen for rendering said image of said record visible to an observer, whereby said image on said viewing screen is in terms of radiation directed to said viewing screen by said reflex reflecting stratum and said visible record is capable of being viewed directly in terms of diflusely scattered radiation not controlled by said reflex reflecting stratum.

6. The system of claim wherein each of said multiplicity of minute increments includes a refracting microsphere.

7. The system of claim 5 wherein each of said multiplicity of minute increments constitutes a corner reflector.

8. A projection system comprising means including a sheet having, as optical components of said sheet in optical communication, a representation and a multiplicity of minute reflex reflecting elements, said multiplicity of minute reflex reflecting elements establishing a selected substantially common path for an incident ray of radiation directed toward said representation and for a resulting ray of radiation redirected by said multiplicity of reflex reflecting elements, said path characteristically being substantially dependent upon the direction of said incident ray and characteristically being substantially independent of the angle of incidence between said incident ray and said sheet, means for directing such radiation into said path from a source, and means for projectnig an image of said representation in terms of such radiation, said elements each including a catadioptric association of refractings lens means for focusing an incident ray from substantially one direction and reflective interface means for redirecting a resulting ray in substantially the opposite direction.

9. A projection system comprising means including a sheet having, as optical components of said sheet in optical communication, a representation and a multiplicity of minute reflex reflecting elements, said multiplicity of minute reflex reflecting elements establishing a selected substantially common path for an incident ray of radiation directed toward said representation and for a resulting ray of radiation redirected by said multiplicity of reflex reflecting elements, said path characteristically being substantially dependent upon the direction of said incident ray and characteristically being substantially independent of the angle of incidence between said incident ray and said sheet, means for directing such radiation into said path from a source, and means for projecting an image of said representation in terms of such radiation, said elements substantially being cube corners presenting three reflecting facets lying in intersecting planes.

10. A projection system comprising: means including a sheet having, in optical communication, imprint receptive stratum means and reflex reflecting stratum means, said reflex reflecting stratum means having a multiplicity of minute, substantially spherical, refractingelements, each of said refracting elements characteristically constituting a lens bounded by opposed surfaces, one of said opposed surfaces constituting means for acquiring incident radiation for transmission through said lens, a metallic reflector contiguous with the other of said pair of opposed surfaces, said metallic reflector constituting means for returning resulting radiation for transmission through said lens, said reflex reflecting stratum means establishing a path for said incident and said resulting radiation; a source, means for directing said incident radiation into said path from said source, a viewing screen, and means for directing :said resulting radiation to said viewing screen in order to produce a visual image of said imprint receptive stratum means.

References Cited by the Examiner UNITED STATES PATENTS 574,214 12/1896 Olmsted 88-24 1,460,071 6/ 1923 Merriman 88-24 1,659,176 2/1928 Tillyer 352-233 X 1,854,864 4/1932 Semenitz 352-232 1,897,275 2/1933 Oswald 352-232 1,902,907 3/1933 Semenitz 88-24 1,904,695 4/ 1933 Plies 88-24 1,910,989 5/1933 Hanks 88-24 2,016,333 10/1935 Leeds 40-135 2,026,292 12/1935 Van Der Grinten. 2,042,604 6/1936 King 88-24 2,499,452 3/ 1950 Bonnet 88-1 2,596,394 5/ 1952 Fitzgerald 88-26 2,647,437 8/1953 Bentley et al 88-24 X 2,647,849 8/1953 Douglas et al. 161-165 2,690,967 10/ 1954 Sharples 96-79 2,713,286 7/=1955 Taylor 88-82 2,742,833 4/1956 Evans et al 96-79 2,760,863 8/1956 Plambeck 96-84 2,805,159 9/1957 Unkauf 96-75 2,809,294 10/ 1957 Vyverberg 96-1 X 2,896,507 7/1959 Mast et al 88-61 2,977,850 4/1961 Vanstrum 88-82 3,053,137 9/1962 Loepfe 250-221 3,085,469 3/ 1963 Carlson 88-24 3,087,382 4/ 1963 De Nygorden 88-24 X 3,095,301 6/1963 Kostelec et a1 96-1 3,096,176 7/1963 Craig 88-24 FOREIGN PATENTS 25,165 of 1907 Great Britain. 870,325 6/ 1961 Great Britain. 891,992 3/ 1962 Great Britain.

OTHER REFERENCES Illumination Engineering Society Lighting Handbook, 3d Ed., N.Y., Illuminating Engineering Society, 1962, pages 310, 311.

NORTON ANSHER, Primary Examiner. 

1. A PROJECTION SYSTEM COMPRISING MEANS INCLUDING A SHEET HAVING, AS COMPONENTS OF SAID SHEET IN OPTICAL COMMUNICATION, A REPRESENTATION AND A MULTIPLICITY OF MINUTE REFLEX REFLECTING ELEMENTS, SAID MULTIPLICITY OF MINUTE REFLEX FEFLECTING ELEMENTS EACH INHERENTLY INCLUDING MEANS FOR ACQUIRING ICIDENT RADIATION FROM SUBSTANTIALLY ANY ONE OF A MULTIPLICITY OF INWARD DIRECTIONS AND MEANS FOR REDIRECTING RESULTING RADIATION IN SUBSTANTIALLY THE OPPOSITE ON E OF A MULTIPLICITY OF OUTWARD DIRECTIONS FOR THE PURPOSE OF ESTABLISHING A SELECTED SUBSTANTIALLY COMMON PATH FOR AN ICIDENT RAY OF RADIATION DIRECT TOWARD SAID REPRESENTATION AND FOR A RESULTING RAY OF RADIATION REDIRECTED BY SAID MULTIPLICITY OF REFLEX REFLECTING ELEMENTS, SAID PATH CHARACTERISTICALLY BEING SUBSTANTIALLY DEPENDENT UPON THE DIRECTION OF SAID INCIDENT RAY AND CHARACTERISTICALLY BEING SUBSTANTIALLY INDEPENDENT OF THE ANGLE OF INCIDENCE BETWEEN SAID INCIDENT RAY ANS SAID SHEET, MEANS FOR DIRECTING SUCH RADIATION INTO SAID PATH FROM A SOURCE, AND MEANS FOR PROJECTING AN IMAGE OF SAID REPRESENTATION ONTO A VIEWING SCREEN IN TERMS OF SUCH RADIATION. 